No abstract

1 The interaction between As and three toxic metals (Cd, Ni and Pb) and Cu (an essential trace metal) in the kidney was investigated in the rat by feeding diets containing various concentrations of As whilst maintaining constant concentrations of the other elements. After 1, 3, 7 and 15 weeks of feeding, metal contents in the renal cortex and medulla, red blood cells and plasma were determined by atomic emission spectrometry (ICP-AES). 2 As accumulated in the whole kidney, whereas Cu accumulated only in the cortex. Accumulation of Cu was found to depend on the feeding period and dietary As concentration. 3 As was also accumulated in red blood cells, where saturation was found at 550 μg As g-1 cells. 4 Although Cd was also accumulated in the cortex, its accumulation was independent of the dietary As concentration. Ni and Pb were not detected by ICP-AES. 5 Chromatography of the supernatants from cortical homogenates of control and As-treated rat kidney suggested that Cu accumulated in renal metallothionein (MT). Its accumulation in this fraction was independent of that of Cd, indicating that the As-Cu interaction was not a result of MT induction, but rather that it might result from altered renal handling of Cu with subsequent incorporation into MT.

To check the hypothesis that adequate dietary iron supplementation reduces cadmium retention and cadmium-induced anaemia during fast growth, three different dietary iron concentrations (6 mg/kg = iron-deficient; 55 mg/kg = marginal iron supply; 180 mg/kg = luxurious iron supply) were offered to growing rats. Four groups of rats at different age (44 days approximately = 150 +/- 6 g, 49 days approximately = 180 +/- 3 g, 57 days approximately = 220 +/- 4 g, and 84 days approximately = 295 9 g) received a diet with 55 mg Fe/kg which is a marginal iron-supply during growth. Six animals in each age group were exposed to 10 mg Cd/l as CdCl2 in the drinking water for 1 week; six animals in each age group received no cadmium. In the youngest and oldest groups additional 6 animals were exposed to the same cadmium dose but received an iron-deficient (6 mg Fe/kg) and an iron-adequate diet (180 mg Fe/kg) together with corresponding controls. The state of iron repletion was monitored by the tissue iron content in liver, kidney, and duodenum as well as by the concentrations of haemoglobin, plasma iron and plasma transferrin. The youngest animals showed the highest percent weight increases. Cadmium administration influenced neither growth rates nor food and water intake. At a dietary iron content of 55 mg/kg, iron repletion was negatively correlated to growth while the cadmium content in liver and kidney showed a positive correlation. At fast growth, a dietary iron content of 6 mg/kg lead to iron-deficiency anaemia and high cadmium retention. At all dietary iron concentrations, cadmium retention as well as the cadmium-related reduction in haemoglobin concentration was significantly higher at fast growth. Adequate dietary iron supplementation reduced cadmium retention and cadmium-induced anaemia significantly. Thus, the delicate balance between iron supply and the increased iron demand during growth can be disturbed within one week by a daily cadmium intake as low as 0.7-1.3 mg Cd/kg body weight.